Hailstone sequence: Difference between revisions

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<lang haskell>import Data.List (maximumBy)

import Data.Ord (comparing)

-------------------- HAILSTONE SEQUENCE ------------------

collatz :: Int -> Int

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longestChain =

fst $

maximumBy (comparing snd) $ ~~(,) <*> (length . hailstone) <$> [1 .. 100000]~~

maximumBy (comparing snd) $

(,) <*> (length . hailstone) <$> [1 .. 100000]

--------------------------- TEST -------------------------

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mapM_

putStrLn

[ "Collatz sequence for 27: "

[ "Collatz sequence for 27: ",

, (show . hailstone) 27

(show . hailstone) 27,

, "The number " <> show longestChain

"The number " <> show longestChain,

, "has the longest hailstone sequence ~~for any number less then 100000.~~ "

"has the longest hailstone sequence",

"for any number less then 100000. ",

⚫

, ~~"The~~ ~~sequence~~ ~~has length: "~~ <> (show . length . hailstone $ longestChain)

"The sequence has length: "

⚫

<> (show . length . hailstone $ longestChain)

]</lang>

<pre>Collatz sequence for 27:

[27,82,41,124,62,31,94,47,142,71,214,107,322,161,484,242,121,364,182,91,274,137,412,206,103,310,155,466,233,700,350,175,526,263,790,395,1186,593,1780,890,445,1336,668,334,167,502,251,754,377,1132,566,283,850,425,1276,638,319,958,479,1438,719,2158,1079,3238,1619,4858,2429,7288,3644,1822,911,2734,1367,4102,2051,6154,3077,9232,4616,2308,1154,577,1732,866,433,1300,650,325,976,488,244,122,61,184,92,46,23,70,35,106,53,160,80,40,20,10,5,16,8,4,2]